When crocheting a hat, how long does it take to get the rippling to stop?

i'm on my first hat and it just keeps furling up into this weird rippled thing that can in no way resemble a hat. LOL isnt it supposed to start looking like a circle? the only think i can think of is that i missed a few stitches or that i'm holding my yarn too tight. the "circle" is about as big as my palm now.